Switchboard and rheostat.



B. M. CRANE. SWITOHBOARD AND RHEOSTAT.

APPLIGA'I'ION FILED MAR. 22, 1909.

Patented Aug. 20, 1912.

2 BHBETB-SHEET 1. lm

0000 0 W 0000 Z\ O m 0000 0 0 0000 0 0000. 0 0000 9 0 E. M. CRANE. SWITGHBOARD AND RHEOSTAT.

APPLIGATIOE FILM) MAR. 22, 1909.

2 SHEETB-SHEET 2.

14! n asses Patented Aug. 20, 1912.

UNITED sTATEs PATENT oEEIoE.

ERNEST M. CRANE, or DETROIT, MICHIGAN, ASSIGNQR '1'0 PELTON & CRANE, or DETROIT, MICHIGAN, A COPARTNERSHIP.

Specification of Letters Patent.

Patented Aug. 20, 1912.

Application. filed March 22, 1909. Serial K0..484,990.

To all whom it may concern:

Be it known that I, ERNEST M. CRANE, a

.citizen of the United States of America,

residing at Detroit, in the county of \Vayne and State of Michigan, have invented cer- 'tain new and useful Improvements in quiring different voltages and comparatively small current volume.

The invention is more particu-l arlydesigned for use in dental laboratories where, in addition to various small motors, such instruments as the mouth lamp, cautery, root canal drier, electric furnaces arefrequently used.

The invention consists in the peculiar construction of the rheostat, and, further, in its peculiar arrangement and combination with a switchboard as hereinafter set forth.

In the drawingsFigure 1 is a front elevation of the board; Fig. 2 is a rear elevation thereof; Fig. 3 is a vertical longitudinal section; Fig. 4 is a sectional perspective view of aportion of the variable rheostat; and Fig. 5 is a diagram showing the operation of the rheostat.

A is the boardwhich is formed of marble, slate or other insulating and noncombustible material.

B is a rectangular. supportin frame to which the board A is secured an by means of which it may -be attached to the wall or in any other convenient location. The frame B is of sufiicient depth to form between the rear face of the board. and the wall a chamber in which the rheostat i-s located, this being of the following. construction: C is a fixed resistance bein formed of a plurality of parallel coils 0 suitable resistance wire wound upon insulati noncombustible cores a and inclosed wit in an open-work metallic case b. This resistance C is preferably arranged to extend across the u per portion oft e board between the opposite sides of the rectangular frame B. D is a variable resistance, which is preferably formed of a coili of resistance wire wound upon an annular core c; and embedded in. an insulating bod/y d within, an annular metallic frame e. The arrangement is such that a small portion of the face of the coils isexposed on one side of the annular frame 6 and is adapted for connection with a traveling contact member E. This traveling contact member is secured to a radial arm F which is attached to a shaft G extending throuh the board and provided with an operating knob or handle H on the front side thereof. There is also provided an index hand I which is arranged opposite the radial arm F and indicates the position of the latter on an annular scale J. In addition to the resistances C and D a third resistance K similar in construction to;.C is preferably arranged across the lower portion of the board.

Upon the front side of the board are arranged th terminal connections for the various electric-at work circuits and as illustra-ted a, plurality of pairs of binding posts,

1, 2, 3, etc., are arranged along the marginal portion of the board. The main leads for the current supply are connected to terminals L, L, at the upper end of the board, and a lamp M is preferably arranged between these terminals for indicating the operative condition of the board. Below the lamp are arranged aseries of safety cutout fuses N controlling respectively the circuits connected to the terminals, 1 to 6, all of which are for the full voltage. Below the cut-outs is-arranged. a series of switches O for controlling the several circuits'i to 6. The knob H, index I and annular scale J occupy the central portion of the board, and below these is a plurality of switches P for controlling the low voltage circuits connected to the terminals '1, 8,. etc. As in most dental laboratories compressed air is used, I preferably employ the lower end of the board for mounting the pressure gages Q, Q, the pressure regulator R, and the distributing. connections S S-' The pneumatic connections between these various devices are arranged in rear of the board and in. the space inclosed by the frame B.

The electric connections between the main lead terminals L L, and thevarious full voltage terminals, 1 to- 6, may be arranged; in

any convenient manner in the rear of the board. The connections between the low voltage terminals, Etc. 10;. andthe rheostat are daagrammatically illustrated. in Fig. 5,

and are arranged as follows: The resistances C and D arepermanently connected in series. with each other and between the main leads, being controlled, however, by the switches P. As shown, the terminal L is connected by a conductor T to one end of the resistance C, while the opposite end of said resistance is connected by a conductor U with one 'end of the resistance D. The opposite end The resistance K is connected by the conductor T to the terminal L and at its opposite end by the conductor Y to a segmental contact member Z arranged parallel to a portion of the variable resistance D. There are also connections T between the travel- .ing contact member E and one set of the members of the work circuit terminals 7, 8, 9 and 10, while the other members of these terminals are individually connected by the conductors P with the corresponding contacts P, P-', P, P' of the switches P.-

The rheostat is of that type in which the resistance is arranged in shunt with the work circuit. 'YVhen the traveling contact E is arranged, as illustrated in dotted lines in Fig. 5, and any one of these switches P is closed, the potential of the work circuit terminals controlled by said switch will be the same, and consequently there will be no flow of the currentthrough the circuit. This is for the reason that when one of the switches P is closed, such as that which con- Qnects the contacts P P, and P, the lead L will be directly connected to the conductor W, which is connected to that end of the re sistance where the arm F is shown in dotted lines. Consequently, the upper member of the terminal 8, which is connected by the conductor T with the arm F, will be at the potential of the lead L, while the lower member of the terminal 8, which is connected by the conductor P with the contact P, will .be at the same potential. As a member E is moved counter clockwise around the variable resistance D by the operation of the'handle H a progressively increasing difierence of potential in the work circuit terminals is produced until said contact reaches the point f, as indicated in full lines in Fig. 5. At this point the contact member E comes into contact with the segmental contact member Z, which throws the resistance K in parallel with the resistance C and in multiple series with a portion of the resistance D. Thus, tracing from the lead L, the current passes through the conductor X, switch. P to the contact P, and through the conductor W to one end of the resistance D; thence through the said re-v sistance to the point f, which is connected by the traveling arm F and conductor T to the upper member of the terminals 8.

From the point f, the circuits continue branch connection established from the point f through the arm F, contact Z, conductor Y to the resistance K, and through the conductors T and T to the lead L. This will greatly increase the current volume flowing between the terminals L, L, but on account of the divided circuits an excessive heating effect in any one portion of the rheostat. is avoided. A further variation of the current in the work circuit may be produced by a movement of the member E over the remaining port-ion D of the resistance D, which portion is preferably made of heavier wire to safely carry the increased current volume.

The switches P, as will be observed, are of the three-pole type, and perform the double function of closing the circuit through the rheostat and also connecting in shunt therewith a particular one of the work circuits 7 to 10. This avoids the necessity of operating two switches and also insures the cutting off of any current whene er the work circuit is opened, thereby av waste. I With the construction as described, :low voltage and comparatively high current in: struments, such as the cautery, may be safely operated, and these are controlled by the same device as is used for controlling instruments operating under higher voltage. The scale J has preferably marked thereon two series of gradations, the one J extending from the zero point to the point f of the resistance, while the end J covers the remaining portion of the resistance and that formed by the heavier wire D. Thus all the advantageof two separate controllers is obtained by the use of a single movable index.

\Vhat I claim as my invention is: v

l. The combination with a switch board, ofa rheostat mounted thereon comprising a fixed resistance, and a variable resistance in series with each other; a work circuit in shunt with said variable resistance, a controller for varying the resistance, and a second fixed resistance adapted to be cut in the circuit in parallel with said first-mentioned fixed resistance upon the movement of said controller to a predetermined point whereby the current in said work circuit is increased. v

2. The combination with a switch board, of a rheostat comprising two fixed resistances and a variable annular resistancmounted upon diil'erent portions and in rear: of said board, one of said fixed resistances being permanently in series with said variable resistance and the other fixed resistance being normally cut out; a work circuit in shunt with said variable resistance, a rotary controller for said work circuit movable over said variable resistance and a contact cooperating with said controller at one position of adjustmentfor cutting in the second fixed resistance in parallel with the permanently connected fixed resistance, for the purpose described.

3. The combination with a switch board,

of a rheostat comprising two fixed resistances and an annular variable resistance mounted in rear of said board, one of said fixed resistances being permanently in series with said annular variable resistance, a rotatable contact slidable over said annular resistance, a work circuit connected to said ond fixed resistance is coupled in parallel with said first-mentioned fixed resistance and in multiple series with said variable resistance, and work circuitwhen sald rotatable and segmental contacts are coupled.

In testimony whereof I aflix my signature in presence of two itnesses.

ERNEST M. CRANE.

\Vi tnesses NELLIE KINsELLA, JAMES P. BARRY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C." 

